From Problems to Structures: the Cousin Problems and the Emergence of the Sheaf Concept

Abstract. Historical work on the emergence of sheaf theory has mainly concentrated on the topological origins of sheaf cohomology in the period from 1945 to 1950, and on subsequent developments. However, a shift of emphasis both in time-scale and disciplinary context can help gain new insight into the emergence of the sheaf concept. This paper concentrates on Henri Cartan’s work in the theory of analytic functions of several complex variables and the strikingly different roles it played at two stages of the emergence of sheaf theory: the definition of a new structure and formulation of a new research programme in1940-1944; the unexpected integration into sheaf cohomology in 1951-1952. In order to bring this two-stage structural transition into perspective, we will concentrate more specifically on a family of problems, the so-called Cousin problems, from Poincaré (1883) to Cartan. This medium-term narrative provides insight into two more general issues in the history of contemporary mathematics. First, we will focus on the use of problems in theory-making. Second, the history ofthe design of structures in geometrically flavoured contexts – such as for the sheaf and fibre-bundle structures – which will help provide a more comprehensive view of the structuralist moment, a moment whose algebraic component has so far been the main focus for historical work. Content